I have never scored below 40 in GMAT quant (including the mahattan tests, veristas tests, GMAT Test Prep, Actual GMATS)
But my score in the quant section of GMAT club tests have been - 34,33,41 and 30! in that order!
when my accuracy was 38% - I got 33 (500 lvl 71%,600 lvl - 33%,700 lvl - 27%)
when my accuracy was 58% - I got 41 (88%,60%,38%)
when my accuracy was 54% - i got a 30 (57%,46%,64%)
I am yet to take my next GMAT but I have absolutely no idea what to expect!
My standard couldnt have gone below what it was already. And the last three test scores have been after 2 months of preparation.
The pros are that the quality of questions are extremely good, really testing.
But once again, the con is, I am not sure how accurate it is. Of you get a good score, then I am sure you will kickass in the actual test, but it really hurts the confidence if your scores are so low constantly.